Semiconductor device

ABSTRACT

A semiconductor device is disclosed, which includes a first interlayer insulating film, a lower-layer interconnection in a first groove in the first film, a second interlayer insulating film over the first film, having a normal via hole opening to the lower-layer interconnection, a normal plug in the normal hole, a third interlayer insulating film over the second film, having a second groove opening to the normal plug, an upper-layer interconnection in the second groove, and a first dummy plug in a first dummy via hole in the second film, the first dummy via hole opening to one of the lower-layer and upper-layer interconnections, wherein a short side of the first dummy plug is larger than a minimum width of a minimum width interconnection and smaller than a minimum diameter of a minimum diameter via hole and a long side is larger than a shortest length of a shortest length interconnection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2005-010732, filed Jan. 18, 2005,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer interconnection structuresemiconductor device adopting damascene technology, which preventsdegradation of reliability of the interconnection due to stressmigration (SM).

2. Description of the Related Art

When a semiconductor device having a damascene interconnection iscontinuously in operation for a long time, a stress migration isgenerated due to generated heat, which generates voids in a via contactor in a lower-layer interconnection portion under the via contact. Thegeneration of voids decreases the reliability of the damasceneinterconnection reliability. Conventionally, a multi via plug in whichplural via plugs are formed in the same connection portion of theinterconnection is used in order to prevent the deterioration ofdamascene interconnection reliability due to the stress migration (seeJpn. Pat. Appln. KOKAI Publication No. 11-74271). There is also proposeda structure having plural dummy via plugs (see Jpn. Pat. Appln. KOKAIPublication No. 2000-119969). However, in such conventional methods,there is a possibility that voids are generated in the via plug to beconnected or in the lower-layer interconnection portion under the viacontact to be connected, and the deterioration of the damasceneinterconnection reliability is not sufficiently prevented.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda semiconductor device comprising:

a first interlayer insulating film formed on a semiconductor substrate;

a lower-layer interconnection formed in a first groove formed in thefirst interlayer insulating film;

a second interlayer insulating film formed on the first interlayerinsulating film and the lower-layer interconnection, the secondinterlayer insulating film having formed therein a normal via holeopening to the lower-layer interconnection;

a normal plug formed in the normal via hole;

a third interlayer insulating film formed on the second interlayerinsulating film and the normal plug, the third interlayer insulatingfilm having formed therein a second groove opening to the normal plug;

an upper-layer interconnection formed in the second groove formed in thethird interlayer insulating film; and

a first dummy plug embedded in a first dummy via hole formed in thesecond interlayer insulating film, the first dummy via hole opening toone of the lower-layer interconnection and the upper-layerinterconnection,

wherein a short side of the first dummy plug in a plan pattern is largerthan a minimum width of a minimum width interconnection and smaller thana minimum diameter of a minimum diameter via hole and a long side of thefirst dummy plug in the plan pattern is larger than a shortest length ofa shortest length interconnection.

According to a second aspect of the present invention, there is provideda semiconductor device comprising:

a first interlayer insulating film formed on a semiconductor substrate;

a lower-layer interconnection formed in a first groove formed in thefirst interlayer insulating film;

a second interlayer insulating film formed on the first interlayerinsulating film and the lower-layer interconnection, the secondinterlayer insulating film having a normal via hole, a dummy via hole,and a second groove, the normal via hole and the dummy via hole openingto the lower-layer interconnection, and the second groove opening to thenormal via hole;

an upper-layer interconnection formed in the normal via hole and thesecond groove formed in the second interlayer insulating film; and

a dummy plug embedded in the dummy via hole formed in the secondinterlayer insulating film,

wherein a short side of the dummy plug in a plan pattern is larger thana minimum width of a minimum width interconnection and smaller than aminimum diameter of a minimum diameter via hole and a long side of thedummy plug in the plan pattern is larger than a shortest length of ashortest length interconnection.

According to a third aspect of the present invention, there is provideda semiconductor device comprising:

a first interlayer insulating film formed on a semiconductor substrate;

a first plug formed in a first via hole formed in the first interlayerinsulating film;

a second interlayer insulating film formed on the first interlayerinsulating film and the first plug;

a normal interconnection formed in a first groove formed in the secondinterlayer insulating film and connected to the first plug;

a second plug formed on the normal interconnection formed in the secondinterlayer insulating film; and

a dummy interconnection formed in a second groove formed in a region ofthe second interlayer insulating film, which corresponds to other regionthan those where the first plug and the second plug are formed, thedummy interconnection being connected to a first embedded metal of thenormal interconnection,

wherein the dummy interconnection has a width which is smaller than aminimum width of a minimum width interconnection.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross sectional view of a semiconductor device in amanufacturing process according to a first embodiment of the presentinvention;

FIG. 2 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 1,according to the first embodiment of the present invention;

FIG. 3 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 2,according to the first embodiment of the present invention;

FIG. 4 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 3,according to the first embodiment of the present invention;

FIG. 5 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 4,according to the first embodiment of the present invention;

FIG. 6 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 5,according to the first embodiment of the present invention;

FIG. 7 shows a plan pattern of a dummy plug 22 b formed in a slit-shapeddummy via hole 19 b of the semiconductor device shown in FIG. 3 and FIG.4 y;

FIG. 8 is a cross sectional view of a semiconductor device in amanufacturing process according to a second embodiment of the presentinvention;

FIG. 9 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 8,according to the second embodiment of the present invention;

FIG. 10 is a cross sectional view of a semiconductor device in amanufacturing process according to a third embodiment of the presentinvention;

FIG. 11 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 10,according to the third embodiment of the present invention;

FIG. 12 is a cross sectional view of a semiconductor device in amanufacturing process according to a fourth embodiment of the presentinvention;

FIG. 13 is a cross sectional view of the semiconductor device in amanufacturing process following the manufacturing process of FIG. 12,according to the fourth embodiment of the present invention;

FIG. 14 is a cross sectional view of a semiconductor device in amanufacturing process according to a fifth embodiment of the presentinvention;

FIG. 15 is a plan pattern of a normal interconnection and a dummyinterconnection of a semiconductor device in a manufacturing processaccording to a sixth embodiment of the present invention;

FIG. 16 is a plan pattern of the normal interconnection and the dummyinterconnection of the semiconductor device in a manufacturing processfollowing the manufacturing process of FIG. 15, according to the sixthembodiment of the present invention;

FIG. 17 is a plan pattern of the normal interconnection and the dummyinterconnection of the semiconductor device in a manufacturing processfollowing the manufacturing process of FIG. 16, according to the sixthembodiment of the present invention; and

FIG. 18 is a cross sectional view of the semiconductor device shown inFIG. 17.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below withreference to the accompanying drawings.

FIG. 1 to FIG. 6 are sectional views of a semiconductor device inmanufacturing processes according to a first embodiment of the presentinvention. FIG. 7 shows a plan pattern of a dummy plug 22 b formed in aslit-shaped dummy via hole 19 b of the semiconductor device according tothe first embodiment of the present invention.

Referring to FIG. 1, a first interlayer insulating film 12 is formed ona semiconductor substrate 11. A second interlayer insulating film 13 isformed on the first interlayer insulating film 12. A lower-layerinterconnection 16 composed of a first barrier metal layer 14 and afirst embedded metal layer 15 is formed in the second interlayerinsulating film 13 by the damascene method. For example, the firstbarrier metal layer 14 is made of Ti (titanium) and the first embeddedmetal layer 15 is made of Cu (copper).

Referring to FIG. 2, a Cu diffusion preventing insulating film 17 isdeposited on the lower-layer interconnection 16 and the secondinterlayer insulating film 13 in order to prevent Cu diffusion from theembedded metal layer 15. A third interlayer insulating film 18 isdeposited on the Cu diffusion preventing insulating film 17.

Referring to FIG. 3, a normal via hole 19 a and a dummy via hole 19 bare formed in the third interlayer insulating film 18 and the insulatingfilm 17 by lithography. The normal via hole 19 a and the dummy via hole19 b are provided on the lower-layer interconnection 16 to open to thelower-layer interconnection 16.

Referring to FIG. 7, the dummy via hole 19 b has a slit shape in a planpattern. The slit-shaped dummy via hole 19 b is shown in the lengthwisedirection thereof in FIG. 7. A short-side length of the slit-shapeddummy via hole 19 b in the plan pattern is larger than a minimum widthof a minimum width interconnection and smaller than a minimum diameterof a minimum-diameter via hole. A long-side length of the dummy via hole19 b in the plan pattern is larger than a shortest length of a shortestlength interconnection. For example, when the minimum diameter of aminimum-diameter via hole is 120 nm in a certain generation, theinterconnection of the same generation can be formed in the width of 90nm and the length of 200 nm. The plan pattern of the normal via hole 19a is in a substantially circular shape which is of a general shape.

Since the dummy via hole 19 b is patterned in the slit shape, etching isdegraded in making the dummy via hole 19 b by the lithography, whichforms a portion broken by over-etching in a portion of the lower-layerinterconnection 16 under a corner portion of a bottom portion of theslit-shaped dummy via hole 19 b. That is, in order to create the portionbroken by the over-etching in a portion of the lower-layerinterconnection 16 under the corner portion of the bottom portion of thedummy via hole 19 b, the plan pattern of the dummy via hole 19 b isshaped in the slit shape and the dummy via hole 19 b is defined in theabove dimensions.

Referring to FIG. 4, a normal plug 22 a and a dummy plug 22 b are formedin the normal via hole 19 a and the dummy via hole 19 b, respectively,by the damascene method. Each of the normal plug 22 a and the dummy plug22 b is comprised of a second barrier metal layer 20 and a secondembedded metal layer 21. For example, the second barrier metal layer 20is made of Ti like the first barrier metal layer 14, and the secondembedded metal layer 21 is made of Cu like the first embedded metallayer 15.

As described above, since the short-side length of the slit-shaped dummyvia hole 19 b in the plan pattern is larger than the minimum width ofthe minimum width interconnection and smaller than the minimum diameterof the minimum-diameter via hole, the short-side length of theslit-shaped dummy via plug 22 b in the plan pattern also is larger thanthe minimum width of the minimum width interconnection and smaller thanthe minimum diameter of the minimum-diameter via hole. Also, asdescribed above, since the long-side length of the dummy via hole 19 bin the plan pattern is larger than the shortest length of the shortestlength interconnection, the long-side length of the dummy plug 22 b inthe plan pattern is also larger than the shortest length of the shortestlength interconnection.

Since the dummy via hole 19 b has a slit shape in the plan pattern, itis difficult that a material of the second barrier metal layer 20 isuniformly formed into a deep portion of the dummy via hole 19 b.Therefore, a film thickness of the barrier metal layer 20 formed on thesurface of the dummy via hole 19 b becomes uneven, and film qualitybecomes coarse. Consequently, bonding between the barrier metal layer 20in the dummy via hole 19 b and the third interlayer insulating film 18is low. Also, bonding between the barrier metal layer 20 in the dummyvia hole 19 b and the Cu diffusion preventing insulating film 17 is low.Further, bonding between the barrier metal layer 20 in the dummy viahole 19 b and the lower-layer interconnection 16 is low.

Since the dummy via hole 19 b is in the slit shape, it is difficult thatthe material of the second metal layer 21 is satisfactorily embeddedinto the deep portion of the dummy via hole 19 b. Therefore, the filmquality of the second embedded metal layer 21 formed in the dummy viahole 19 b becomes uneven and coarse. Therefore, the bonding between thesecond embedded metal layer 21 and the second barrier metal layer 20 inthe dummy via hole 19 b is low.

Referring to FIG. 5, a fourth interlayer insulating film 23 is depositedon the normal plug 22 a, the dummy plug 22 b, and the third interlayerinsulating film 18.

Referring to FIG. 6, interconnection grooves 41 a and 41 b are formed inthe fourth interlayer insulating film 23. The interconnection grooves 41a and 41 b are formed at portions of the fourth interlayer insulatingfilm 23, which do not correspond to the dummy plug 22 b. Theinterconnection groove 41 a corresponds to the normal plug 22 a andopens to the normal plug 22 a. Then, upper-layer interconnections 26 aand 26 b are formed in the interconnection grooves 41 a and 41 b,respectively, by the damascene method. Each of the upper-layerinterconnections 26 a and 26 b is formed of a third barrier metal layer24 and a third embedded metal layer 25. Since the interconnectiongrooves 41 a and 41 b are formed at portions of the fourth interlayerinsulating film 23, which do not correspond to the dummy plug 22 b, theupper-layer interconnections 26 a and 26 b are not connected to thedummy plug 22 b. Since the interconnection groove 41 a opens to thenormal plug 22 a, the upper-layer interconnection 26 a is connected tothe normal plug 22 a.

In the first embodiment, the slit-shaped dummy plug 22 b is provided sothat a portion of the lower-layer interconnection 16 under the cornerportion of the bottom portion of the dummy plug 22 b is damaged andbroken by the over-etching. The stress migration easily occurs in thebroken portion. The occurrence of the stress migration in the brokenportion suppresses the generation of the stress migration in the normalplug 22 a and in the portion of the lower-layer interconnection 16 underthe corner portion of the bottom portion of the normal plug 22 a. As aresult, the generation of voids is suppressed in the normal plug 22 aand in the portion of the lower-layer interconnection 16 under thecorner portion of the bottom portion of the normal plug 22 a, whichallows the normal plug 22 a to satisfactorily connect the lower-layerinterconnection 16 to the upper-layer interconnection 25.

AS described above, according to the first embodiment, the slit-shapeddummy plug 22 b is provided. As a result, the generation of the stressmigration in the normal plug 22 a and in the portion of the lower-layerinterconnection 16 under the corner portion of the bottom portion of thenormal plug 22 a is suppressed, with the result that the generation ofvoids in the normal plug 22 a and in the portion of the lower-layerinterconnection 16 under the corner portions of the bottom portion ofthe normal plug 22 a is suppressed. Accordingly, the normal plug 22 asatisfactorily connects the lower-layer interconnection 16 to theupper-layer interconnection 25. This improves the reliability of theinterconnection.

FIG. 8 and FIG. 9 are cross sectional views of a semiconductor device ina manufacturing process according to a second embodiment of the presentinvention. The same components as those in the first embodiment aredesignated by the same numerals, and the description will not berepeated.

In the second embodiment, as shown in FIG. 8, the normal via hole 19 aand the dummy via hole 19 b are formed in the third interlayerinsulating film 18 by the lithography in the same manner as in the firstembodiment. In the second embodiment, a dummy via hole 19 c is formed.The dummy via hole 19 c can be formed simultaneously with the normal viahole 19 a and the dummy via hole 19 b in the same lithography process.The normal via hole 19 a and the dummy via hole 19 b are formed on thelower-layer interconnection 16 and open to the lower-layerinterconnection 16. The dummy via hole 19 c is formed on the secondinterlayer insulating film 13 and opens to the second interlayerinsulating film 13.

As described in the first embodiment, the dummy via hole 19 b is shapedin a form of slit in the plan pattern. The short-side length of theslit-shaped dummy via hole 19 b in the plan pattern is larger than theminimum width and smaller than the minimum width interconnection to theminimum diameter of the minimum-diameter via hole. The long-side lengthof the dummy via hole 19 b in the plan pattern is larger than theshortest length of the shortest length interconnection. Similarly to thenormal via hole 19 a, the plan pattern of the dummy via hole 19 c ismade in the substantially circular shape which is the general shape. Thedimensions of the dummy via hole 19 c may be the same as or differentfrom the dimensions of the normal via hole 19 a. However, in order tosimplify a mask manufacturing process, the dimensions of the dummy viahole 19 c are preferably the same as the dimensions of the normal viahole 19 a.

In the second embodiment, also, the portion broken by the over-etchingis formed in the portion of the lower-layer interconnection 16 under thecorner portion of the bottom portion of the slit-shaped dummy via hole19 b like the first embodiment.

Since the second interlayer insulating film 13 is etched more easilythan the lower-layer interconnection 16, a portion of the secondinterlayer insulating film 13 under the corner portion of the bottomportion of the circular dummy via hole 19 c is broken to form the brokenportion by the over-etching in the lithography process.

Referring to FIG. 9, plugs 22 a, 22 b, and 22 c are formed in the normalvia hole 19 a, the dummy via hole 19 b, and the dummy via hole 19 c,respectively, by the damascene method. Each of the plugs 22 a, 22 b, and22 c is composed of the second barrier metal layer 20 and the secondembedded metal layer 21. The plug 22 b and the plug 22 c are dummyplugs.

As described in the first embodiment, since the dummy via hole 19 b ismade in the slit shape, it is difficult that the material of the secondbarrier metal layer 20 is uniformly formed into the deep portion of thedummy via hole 19 b. Therefore, the film thickness of the barrier metallayer 20 formed on the surface of the dummy via hole 19 b becomes unevenand the film quality also becomes coarse. Consequently, bonding betweenthe barrier metal layer 20 in the dummy via hole 19 b and the thirdinterlayer insulating film 18 is low. Also, bonding between the barriermetal layer 20 in the dummy via hole 19 b and the Cu diffusionpreventing insulating film 17 is low. Further, bonding between thebarrier metal layer 20 in the dummy via hole 19 b and the lower-layerinterconnection 16 is low.

Also, as described in the first embodiment, since the dummy via hole 19b is made in the slit shape, it is difficult that the material of thesecond metal layer 21 is satisfactorily embedded into the deep portionof the dummy via hole 19 b. Therefore, the film quality of the secondembedded metal layer 21 becomes coarse. Therefore, the bonding betweenthe second embedded metal layer 21 and the second barrier metal layer 20in the dummy via hole 19 b is low.

In the second embodiment, as shown in FIG. 9, an upper-layerinterconnection 27 is formed on the third interlayer insulating film 18unlike the first embodiment, and the upper-layer interconnection 27 isconnected to the normal plug 22 a and the dummy plugs 22 b and 22 c. Inthe second embodiment, the same effects as those in the first embodimentare obtained by the dummy plug 22 b. That is, in the second embodiment,the dummy plug 22 b is provided so that a portion of the lower-layerinterconnection 16 under the corner portion of the bottom portion of thedummy plug 22 b is broken, with the result that the stress migration isgenerated by the broken portion. Therefore, the generation of the stressmigration is suppressed in the portion of the lower-layerinterconnection 16 under the bottom portion of the normal plug 22 a andthus the void generation is suppressed in the normal plug 22 a and inthe portion of the lower-layer interconnection 16 under the cornerportions of the bottom portion of the normal plug 22 a.

Further, in the second embodiment, since the upper-layer interconnection27 is connected to the dummy plug 22 b, the stress migration isgenerated in the dummy plug 22 b due to the coarseness of the dummy plug22 b, which generates voids in the dummy plug 22 b. The generation ofthe stress migration in the dummy plug 22 b further suppresses thegeneration of the stress migration in the normal plug 22 a or in theportion of the lower-layer interconnection 16 of the bottom portion ofthe normal plug 22 a, which suppresses the void generation in the normalplug 22 a or in the portion of the lower-layer interconnection 16 of thebottom portion of the normal plug 22 a.

Further, in the second embodiment, since the broken portion is formed inthe portion of the second interlayer insulating film 13 under the cornerportion of the bottom portion of the dummy plug 22 c, the stressmigration is also generated in the broken portion. Accordingly, thegeneration of the stress migration is further suppressed in the normalplug 22 a or in the portion of the lower-layer interconnection 16 of thebottom portion of the normal plug 22 a, with the result that the voidgeneration in the normal plug 22 a or in the portion of the lower-layerinterconnection 16 of the bottom portion of the normal plug 22 a issuppressed.

Thus, according to the second embodiment, provision of the dummy plug 22c further suppresses the generation of the stress migration in thenormal plug 22 a or in the portion of the lower-layer interconnection 16under the bottom portion of the normal plug 22 a. Therefore, the normalplug 22 a further satisfactorily connects the lower-layerinterconnection 16 to the upper-layer interconnection 25 to furtherimprove the reliability of the interconnection.

FIG. 10 and FIG. 11 are cross sectional views of a semiconductor devicein a manufacturing process according to a third embodiment of thepresent invention. The same components as those in the first embodimentare designated by the same numerals, and the description will not berepeated.

In the third embodiment, as shown in FIG. 10, the normal via hole 19 aand the dummy via hole 19 b are formed in the third interlayerinsulating film 18 by the lithography in the same manner as in the firstembodiment. Also, in the third embodiment, a dummy via hole 19 d isfurther formed. The dummy via hole 19 d can be formed simultaneouslywith the normal via hole 19 a and the dummy via hole 19 b in the samelithography process. The normal via hole 19 a and the dummy via hole 19b are formed on the lower-layer interconnection 16 and open to thelower-layer interconnection 16. The dummy via hole 19 d is formed on thesecond interlayer insulating film 13 and opens to the second interlayerinsulating film 13.

As described in the first embodiment, in the dummy via hole 19 b, theplan pattern is made in the slit shape. The short-side length of theslit-shaped dummy via hole 19 b in the plan pattern is larger than theminimum width of the minimum width interconnection and smaller than theminimum diameter of the minimum-diameter via hole. The long-side lengthof the dummy via hole 19 b in the plan pattern is larger than theshortest length of the shortest length interconnection. The plan patternof the normal via hole 19 a is made in the substantially circular shapewhich is the general shape.

Similarly to the dummy via hole 19 b, in the dummy via hole 19 d, theplan pattern is made in the slit shape. Similarly to the slit-shapeddummy via hole 19 b, the short-side length of the slit-shaped dummy viahole 19 d in the plan pattern is larger than the minimum width of theminimum width interconnection and smaller than the minimum diameter ofthe minimum-diameter via hole. The long-side length of the dummy viahole 19 d in the plan pattern is also larger than the shortest length ofthe shortest length interconnection. The dimensions of the via hole 19 dmay be the same as or different from the dimensions of the via hole 19b. However, in order to simplify the mask manufacturing process, thedimensions of the via hole 19 c are preferably the same as thedimensions of the via hole 19 b.

In the third embodiment, the portion broken by the over-etching is alsoformed in the portion of the lower-layer interconnection 16 under thecorner portion of the bottom portion of the slit-shaped dummy via hole19 b during the lithography like the first embodiment.

In the third embodiment, the plan pattern of the dummy via hole 19 d isalso formed in the slit shape like the dummy via hole 19 b, so that theportion of the second interlayer insulating film 13 under the cornerportion of the bottom portion of the dummy via hole 19 d is broken togenerate the broken portion by the over-etching during the lithographyof the dummy via hole 19 d. Since the second interlayer insulating film13 is etched more easily than the lower-layer interconnection 16, thebroken portion formed in the portion of the second interlayer insulatingfilm 13 under the corner portion of the bottom portion of the dummy viahole 19 d is deeper than the broken portion formed in the portion of thesecond interlayer insulating film 13 of the dummy via hole 19 b.

The plugs 22 a, 22 b, and 22 d are formed in the normal via hole 19 a,the dummy via hole 19 b, and the dummy via hole 19 d by the damascenemethod. Each of the plugs 22 a, 22 b, and 22 d is comprised of thesecond barrier metal layer 20 and the embedded metal layer 21. The plug22 b and the plug 22 d are the dummy plugs.

As described in the first embodiment, since the dummy via hole 19 b ismade in the slit shape, it is difficult that the material of the secondbarrier metal layer 20 is uniformly formed into the deep portion of thedummy via hole 19 b. Therefore, the film thickness of the barrier metallayer 20 formed on the surface of the dummy via hole 19 b becomes unevenand the film quality also becomes coarse. Consequently, bonding betweenthe barrier metal layer 20 in the dummy via hole 19 b and the thirdinterlayer insulating film 18 is low. Also, bonding between the barriermetal layer 20 in the dummy via hole 19 b and the Cu diffusionpreventing insulating film 17 is low. Further, bonding between thebarrier metal layer 20 in the dummy via hole 19 b and the lower-layerinterconnection 16 is low.

Also, as described in the first embodiment, since the dummy via hole 19b is made in the slit shape, it is difficult that the material of thesecond metal layer 21 is satisfactorily embedded into the deep portionof the dummy via hole 19 b. Therefore, the film quality of the secondembedded metal layer 21 formed in the dummy via hole 19 b becomescoarse. Consequently, the bonding between the second embedded metallayer 21 and the second barrier metal layer 20 in the dummy via hole 19b is low.

As described above, since the dummy via hole 19 d is made in the slitshape like the dummy via hole 19 b, it is difficult that the material ofthe second barrier metal layer 20 is uniformly formed into the deepportion of the dummy via hole 19 b. Therefore, the film thickness of thebarrier metal layer 20 formed on the surface of the dummy via hole 19 dbecomes uneven and the film quality also becomes coarse. Consequently,bonding between the barrier metal layer 20 in the dummy via hole 19 dand the third interlayer insulating film 18 is low. Also, bondingbetween the barrier metal layer 20 in the dummy via hole 19 d and the Cudiffusion preventing insulating film 17 is low. Further, bonding betweenthe barrier metal layer 20 in the dummy via hole 19 d and thelower-layer interconnection 16 is low. It is also difficult that thematerial of the second embedded metal layer 21 is satisfactorilyembedded into the deep portion of the dummy via hole 19 d. Therefore,the film quality of the second embedded metal layer 21 in the dummy viahole 19 d becomes non-dense. Consequently, the bonding between thesecond embedded metal layer 21 and the second barrier metal layer 20 inthe dummy via hole 19 d is low.

In the third embodiment, as shown in FIG. 10, the upper-layerinterconnection 27 is formed on the third interlayer insulating film 18unlike the first embodiment, and the upper-layer interconnection 27 isconnected to the normal plug 22 a and the dummy plugs 22 b and 22 d.

In the third embodiment, the same effects as those in the firstembodiment are obtained by the dummy plug 22 b. That is, provision ofthe dummy plug 22 b creates the broken portion in the portion of thelower-layer interconnection 16 under the corner portion of the bottomportion of the dummy plug 22 b, and the stress migration is generated bythe broken portion. Therefore, the generation of the stress migration issuppressed in the portion of the lower-layer interconnection 16 of thebottom portion of the normal plug 22 a and the void generation issuppressed in the normal plug 22 a or in the portion of the lower-layerinterconnection 16 under the corner portions of the bottom portion ofthe normal plug 22 a.

Further, in the third embodiment, since the upper-layer interconnection27 is connected to the dummy plug 22 b, the stress migration isgenerated in the dummy plug 22 b due to the coarseness of the dummy plug22 b, which generates the void in the dummy plug 22 b. The generation ofthe stress migration in the dummy plug 22 b suppresses the generation ofthe stress migration in the normal plug 22 a or in the portion of thelower-layer interconnection 16 of the bottom portion of the normal plug22 a, which suppresses the void generation in the normal plug 22 a or inthe portion of the lower-layer interconnection 16 under the cornerportion of the bottom portion of the normal plug 22 a.

Further, in the third embodiment, since the broken portion is formed inthe portion of the second interlayer insulating film 13 under the cornerportion of the bottom portion of the dummy plug 22 d, the stressmigration is also generated in the broken portion. Since the brokenportion formed in the portion of the second interlayer insulating film13 under the corner portion of the bottom portion of the dummy plug 22 dis larger than the broken portion formed in the portion of thelower-layer interconnection 16 under the corner portion of the bottomportion of the plug 22 b, the large stress migration is generated in thebroken portion in the portion of the second interlayer insulating film13 under the corner portion of the bottom portion of the dummy plug 22d. As a result, the generation of the stress migration is furthersuppressed in the normal plug 22 a or in the portion of the lower-layerinterconnection 16 under the corner portion of the bottom portion of thenormal plug 22 a, which suppresses the void generation in the normalplug 22 a or in the portion of the lower-layer interconnection 16 underthe corner portion of the bottom portion of the normal plug 22 a. Sincethe upper-layer interconnection 27 is connected to the dummy plug 22 d,the stress migration toward the upper-layer interconnection 27 isgenerated in the dummy plug 22 d due to the coarseness of the dummy plug22 d, which induces the void in the dummy plug 22 d. As a result, thegeneration of the stress migration is further suppressed in the normalplug 22 a and in the portion of the lower-layer interconnection 16 underthe corner portion of the bottom portion of the normal plug 22 a and thevoid generation is suppressed in the normal plug 22 a and in the portionof the lower-layer interconnection 16 under the corner portion of thebottom portion of the normal plug 22 a. This allows the normal plug 22 ato further satisfactorily connect the lower-layer interconnection 16 andthe upper-layer interconnection 25 to further improve the reliability ofthe interconnection.

FIG. 12 and FIG. 13 are cross sectional views of a semiconductor devicein a manufacturing process according to a fourth embodiment of theinvention. The same components as those in the first, second, and thirdembodiments are designated by the same numerals, and the descriptionwill not be repeated.

In the fourth embodiment, as shown in FIG. 12, the normal via hole 19 aand the dummy via hole 19 b are formed in the third interlayerinsulating film 18 by the lithography in the same manner as in the firstembodiment. Dummy via holes 19 c and 19 d are also formed in the fourthembodiment. The dummy via holes 19 c and 19 d can be formedsimultaneously with the normal via hole 19 a and the dummy via hole 19 bin the same lithography process. The normal via hole 19 a and the dummyvia hole 19 b are formed on the lower-layer interconnection 16 and opento the lower-layer interconnection 16. The dummy via holes 19 c and 19 dare formed on the second interlayer insulating film 13 and open to thesecond interlayer insulating film 13.

As described in the first embodiment, in the dummy via hole 19 b, theplan pattern is made in the slit shape. The short-side length of theslit-shaped dummy via hole 19 b in the plan pattern also is larger thanthe minimum width of the minimum width interconnection and smaller thanthe minimum diameter of the minimum-diameter via hole. The long-sidelength of the dummy via hole 19 b in the plan pattern is also largerthan the shortest length of the shortest length interconnection. Theplan pattern of the normal via hole 19 a is made in the substantiallycircular shape which is of the general shape.

As described in the second embodiment, the plan pattern of the dummy viahole 19 c is made in the substantially circular shape like the normalvia hole 19 a. The dimensions of the dummy via hole 19 c may be same asor different from the dimensions of the normal via hole 19 a. However,in order to simplify the mask producing process, the dimensions of thedummy via hole 19 c are preferably the same as the dimensions of thenormal via hole 19 a. As described in the third embodiment, the planpattern of the dummy via hole 19 d is made in the slit shape like thedummy via hole 19 b. Similarly to the slit-shaped dummy via hole 19 b,the short-side length of the slit-shaped dummy via hole 19 d in the planpattern also is larger than the minimum width of the minimum widthinterconnection and smaller than the minimum diameter of theminimum-diameter via hole. The long-side length of the dummy via hole 19d in the plan pattern is also larger than the shortest length of theshortest length interconnection. The dimensions of the dummy via hole 19d may be the same as or different from the dimensions of the via hole 19b. However, in order to simplify the mask producing process, thedimensions of the dummy via hole 19 d are preferably the same as thedimensions of the via hole 19 b.

Similarly to the first embodiment, the portion of the lower-layerinterconnection 16 under the corner portion of the bottom portion of theslit-shaped dummy via hole 19 b is broken by the over-etching to formthe broken portion in the lithography.

As described in the second embodiment, the portion of the secondinterlayer insulating film 13 under the corner portion of the bottomportion of the circular dummy via hole 19 c is also broken by theover-etching to form the broken portion in the lithography. Since thesecond interlayer insulating film 13 is etched more easily than thelower-layer interconnection 16, the broken portion formed in the portionof the second interlayer insulating film 13 under the corner portion ofthe bottom portion of the dummy via hole 19 c is larger than the brokenportion formed in the portion of second interlayer insulating film 13 ofthe normal via hole 19 a.

In the fourth embodiment, the plan pattern of the dummy via hole 19 d isalso formed in the slit shape like the dummy via hole 19 b, so that theportion of the second interlayer insulating film 13 under the cornerportion of the bottom portion of the dummy via hole 19 d is broken togenerate the broken portion by the over-etching during the lithographyof the dummy via hole 19 d. Since the second interlayer insulating film13 is etched more easily than the lower-layer interconnection 16, thebroken portion formed in the portion of the second interlayer insulatingfilm 13 under the corner portion of the bottom portion of the dummy viahole 19 d is deeper than the broken portion formed in the portion of thesecond interlayer insulating film 13 of the dummy via hole 19 b.

As shown in FIG. 13, the plugs 22 a, 22 b, 22 c, and 22 d are formed inthe normal via hole 19 a, the dummy via hole 19 b, the dummy via hole 19c, and the dummy via hole 19 d by the damascene method. Each of theplugs 22 a, 22 b, 22 c, and 22 d is formed of the second barrier metallayer 20 and the second embedded metal layer 21. The plugs 22 b, 22 d,and 22 d are the dummy plugs.

As described in the first embodiment, since the dummy via hole 19 b hasa slit shape in the plan pattern, it is difficult that a material of thesecond barrier metal layer 20 is uniformly formed into the deep portionof the dummy via hole 19 b. Therefore, a film thickness of the barriermetal layer 20 formed on the surface of the dummy via hole 19 b becomesuneven, and film quality becomes coarse. Consequently, bonding betweenthe barrier metal layer 20 in the dummy via hole 19 b and the thirdinterlayer insulating film 18 is low. Also, bonding between the barriermetal layer 20 in the dummy via hole 19 b and the Cu diffusionpreventing insulating film 17 is low. Further, bonding between thebarrier metal layer 20 in the dummy via hole 19 b and the lower-layerinterconnection 16 is low.

Also, since the dummy via hole 19 b is in the slit shape, as describedin the first embodiment, it is difficult that the material of the secondmetal layer 21 is satisfactorily embedded into the deep portion of thedummy via hole 19 b. Therefore, the film quality of the second embeddedmetal layer 21 formed in the dummy via hole 19 b becomes uneven andcoarse. Therefore, the bonding between the second embedded metal layer21 and the second barrier metal layer 20 in the dummy via hole 19 b islow.

Since the dummy via hole 19 d is made in the slit shape like the dummyvia hole 19 b, it is difficult that the material of the second barriermetal layer 20 is uniformly formed into the deep portion of the dummyvia hole 19 d. Therefore, a film thickness of the barrier metal layer 20formed on the surface of the dummy via hole 19 d becomes uneven, andfilm quality becomes coarse. Consequently, bonding between the barriermetal layer 20 in the dummy via hole 19 d and the third interlayerinsulating film 18 is low. Also, bonding between the barrier metal layer20 in the dummy via hole 19 d and the Cu diffusion preventing insulatingfilm 17 is low. Further, bonding between the barrier metal layer 20 inthe dummy via hole 19 d and the second interlayer insulating film 13 islow.

Also, since the dummy via hole 19 d is made in the slit shape like thedummy via hole 19 b, It is difficult that the material of the secondembedded metal layer 21 is satisfactorily embedded into the deep portionof the dummy via hole 19 d. Therefore, the film quality of the secondembedded metal layer 21 formed in the dummy via hole 19 d becomescoarse. Consequently, the bonding between the second embedded metallayer 21 and the second barrier metal layer 20 in the dummy via hole 19d is low.

As shown in FIG. 13, the upper-layer interconnection 27 is formed on thethird interlayer insulating film 18, and the upper-layer interconnection27 is connected to the normal plug 22 a and the dummy plugs 22 b, 22 c,and 22 d. In the fourth embodiment, the same effects as those in thefirst embodiment are obtained by the dummy plug 22 b. That is, provisionof the dummy plug 22 b creates the broken portion in the portion of thelower-layer interconnection 16 under the corner portion of the bottomportion of the dummy plug 22 b, and the stress migration is generated bythe broken portion. Therefore, the generation of the stress migration issuppressed in the portion of the lower-layer interconnection 16 of thebottom portion of the normal plug 22 a, with the result that the voidgeneration is suppressed in the normal plug 22 a or in the portion ofthe lower-layer interconnection 16 under the corner portions of thebottom portion of the normal plug 22 a.

Further, in the fourth embodiment, since the upper-layer interconnection27 is connected to the dummy plug 22 b, the stress migration isgenerated in the dummy plug 22 b due to the coarseness of the dummy plug22 b, which generates the void in the dummy plug 22 b. The generation ofthe stress migration in the dummy plug 22 b further suppresses thegeneration of the stress migration in the normal plug 22 a or in theportion of the lower-layer interconnection 16 of the bottom portion ofthe normal plug 22 a, which suppresses the void generation in the normalplug 22 a or in the portion of the lower-layer interconnection 16 underthe corner portion of the bottom portion of the normal plug 22 a.

Further, in the fourth embodiment, since the broken portion formed inthe portion of the second interlayer insulating film 13 under the cornerportion of the bottom portion of the dummy plug 22 c is deeper than thebroken portion formed in the portion of the lower-layer interconnection16 under the corner portion of the bottom portion of the dummy plug 22b, the large stress migration is generated in the dummy plug 22 c due tothe coarseness of the dummy plug 22 c. As a result, the generation ofthe stress migration is further suppressed in the normal plug 22 a or inthe portion of the lower-layer interconnection 16 under the cornerportion of the bottom portion of the normal plug 22 a, which suppressesthe void generation in the normal plug 22 a or in the portion of thelower-layer interconnection 16 under the corner portion of the bottomportion of the normal plug 22 a.

Further, in the fourth embodiment, since the broken portion formed inthe portion of the second interlayer insulating film 13 under the cornerportion of the bottom portion of the dummy plug 22 d is deeper than thebroken portion formed in the portion of the lower-layer interconnection16 under the corner portion of the bottom portion of the dummy plug 22b, the large stress migration is generated in the dummy plug 22 d due tothe coarseness of the dummy plug 22 d. As a result, the generation ofthe stress migration is further suppressed in the normal plug 22 a or inthe portion of the lower-layer interconnection 16 under the cornerportion of the bottom portion of the normal plug 22 a, which suppressesthe void generation in the normal plug 22 a or in the portion of thelower-layer interconnection 16 under the corner portion of the bottomportion of the normal plug 22 a.

Thus, according to the fourth embodiment, provision of the dummy plugs22 c and 22 d further suppresses the stress migration in the normal plug22 a or in the portion of the lower-layer interconnection 16 under thecorner portion of the bottom portion of the normal plug 22 a, whichfurther improves the reliability of the interconnection.

FIG. 14 is a cross sectional view showing a semiconductor deviceaccording to a fifth embodiment of the present invention. Thesemiconductor device of the fifth embodiment has a dual damascenestructure. The same components as those in the first embodiment aredesignated by the same numerals, and the description will not berepeated.

The upper-layer interconnections 26 a and 26 b are shown in FIG. 14. Theupper-layer interconnection 26 a and the normal plug 22 a are formed inthe form of the dual damascene structure. The upper-layerinterconnections 26 a and 26 b, the normal plug 22 a and the dummy plug22 b are formed in the third interlayer insulating film 18. In FIG. 14,the interlayer insulating film 18 is formed in a single layer.Alternatively, the interlayer insulating film 18 may be formed in alaminated layer having two or more layers, and the upper-layerinterconnections 26 a and 26 b, the normal plug 22 a and the dummy plug22 b may be formed in the laminated layer. The normal plug 22 a isformed in a via hole formed in a lower-layer portion of the interlayerinsulating film 18, and the upper-layer interconnection 26 a is formedin a groove formed in the upper-layer portion adjacent to thelower-layer portion of the interlayer insulating film 18. The normalplug 22 a is not formed in the lower-layer and the upper-layer portions.

In the fifth embodiment, the dummy plug 22 b is also provided on thelower-layer interconnection 16, and the same effects as those in thefirst embodiment are obtained by the dummy plug 22 b. That is, provisionof the dummy plug 22 b creates the broken portion in the portion of thelower-layer interconnection 16 under the corner portion of the bottomportion of the dummy plug 22 b, and the stress migration is generated bythe broken portion. Therefore, the generation of the stress migration issuppressed in the portion of the lower-layer interconnection 16 of thebottom portion of the normal plug 22 a, and the void generation issuppressed in the normal plug 22 a or in the portion of the lower-layerinterconnection 16 under the corner portions of the bottom portion ofthe normal plug 22, which allows the reliability of the interconnectionto be further improved.

FIG. 15 to FIG. 17 are sectional views of a semiconductor device in amanufacturing process according to a sixth embodiment of the presentinvention. FIG. 18 is a sectional view showing the semiconductor deviceof the sixth embodiment. The same components as those in the firstembodiment are designated by the same numerals, and the description willnot be repeated. In the sixth embodiment, a dummy interconnection isformed. In the structure of the sixth embodiment, the same effect as thefirst embodiment is obtained.

Referring to FIG. 15 and FIG. 18, an interconnection groove is formed inthe second interlayer insulating film 13, and the first barrier metallayer 14 and the interconnection material 15 made of Cu are embedded inthe interconnection groove to form the lower-layer interconnection 16 bythe damascene method. The lower-layer interconnection 16 is connected toa first normal plug 35 formed in the first interlayer insulating film 12formed on the semiconductor substrate 11.

Referring to FIG. 16 and FIG. 18, a dummy interconnection groove 31 isformed in the second interlayer insulating film 13. The dummyinterconnection groove 31 is connected to the interconnection material15 of the lower-layer interconnection 16. The dummy interconnectiongroove 31 is provided in a plan view in the region which does notcorrespond to the first normal plug 35 and a second normal plug 22 a.The dummy interconnection groove 31 has a size smaller than a minimumwidth of a minimum width interconnection in a plan pattern.

Referring to FIG. 17 and FIG. 18, a barrier metal layer 32 and aninterconnection material 33 made of Cu are embedded in the dummyinterconnection groove 31 to form a dummy interconnection 34 by thedamascene method. Since the dummy interconnection groove 31 has a sizesmaller than a minimum width of a minimum width interconnection, thedummy interconnection 34 also has the size smaller than the minimumwidth of the minimum interconnection.

Since the size of the dummy interconnection groove 31 is smaller thanthe minimum width of a minimum width interconnection, it is difficultthat a material of the barrier metal layer 32 is uniformly formed into adeep portion of the dummy interconnection groove 31. Therefore, a filmthickness of the barrier metal layer 32 formed on the surface of thedummy interconnection groove 31 becomes uneven, and film quality becomescoarse. Consequently, bonding between the barrier metal layer 32 in thedummy interconnection groove 31 and the second interlayer insulatingfilm 13 is low. Also, bonding between the barrier metal layer 32 in thedummy interconnection groove 31 and the interconnection material 15 ofthe lower-layer interconnection 16 is low. Further, bonding between thebarrier metal layer 32 in the dummy interconnection groove 31 and thefirst interlayer insulating film 12 is low.

Also, since the size of the dummy interconnection groove 31 is smallerthan the minimum width of a minimum width interconnection, it isdifficult that the material of the interconnection material 33 issatisfactorily embedded into the deep portion of the dummyinterconnection groove 31. Therefore, the film quality of the embeddedinterconnection material 33 formed in the interconnection groove 31becomes uneven and coarse. Therefore, the bonding between the embeddedinterconnection material 33 and the barrier metal layer 32 in the dummyinterconnection groove 31 is low.

In this embodiment, since the dummy interconnection 34 having the sizesmaller than the minimum width of the minimum interconnection isprovided, voids are easily generated in the dummy interconnection 34. Asa result, the stress migration easily occurs in the dummyinterconnection 34, which suppresses the stress migration in the firstand second normal plugs to improve the reliability of theinterconnection.

In the above embodiments, Cu is used as the embedded metal layermaterial. However, the embedded metal layer material is not limited toCu, and another material such as Al (aluminum), Ag (silver), and W(tungsten) which is generally used as the embedded interconnectionmaterial in the field of the semiconductor technology can be used as theembedded metal layer material. The material in which Al (aluminum), Ag(silver), W (tungsten), and the like are added to a principal componentof Cu (copper) may be used as the embedded metal layer material. In theabove embodiments, Ti is used as the barrier metal layer material.However, the barrier metal layer material is not limited to Ti, andanother material such as TiN (titanium nitride) which is usually used asthe barrier metal layer material in the field of the semiconductortechnology can be used as the barrier metal layer material.

1-10. (canceled)
 11. A semiconductor device comprising: a first interlayer insulating film formed on a semiconductor substrate; a lower-layer interconnection formed in a first groove formed in the first interlayer insulating film; a second interlayer insulating film formed on the first interlayer insulating film and the lower-layer interconnection, the second interlayer insulating film having a normal via hole, a dummy via hole, and a second groove, the normal via hole and the dummy via hole opening to the lower-layer interconnection, and the second groove opening to the normal via hole; an upper-layer interconnection formed in the normal via hole and the second groove formed in the second interlayer insulating film; and a dummy plug embedded in the dummy via hole formed in the second interlayer insulating film, wherein a short side of the dummy plug in a plan pattern is larger than a minimum width of a minimum width interconnection and smaller than a minimum diameter of a minimum diameter via hole and a long side of the dummy plug in the plan pattern is larger than a shortest length of a shortest length interconnection.
 12. A semiconductor device according to claim 11, wherein the lower-layer interconnection is formed of a first barrier metal layer and a first embedded metal layer, the upper-layer interconnection is formed of a second barrier metal layer and a second embedded metal layer, and the dummy plug is formed of a third barrier metal layer and a third embedded metal layer.
 13. A semiconductor device according to claim 12, wherein the barrier metal layer of the lower-layer interconnection, the barrier metal layer of the upper-layer interconnection, and the barrier metal layer of the plug is made of Ti or TiN.
 14. A semiconductor device according to claim 12, wherein the embedded metal layer of the lower-layer interconnection, the embedded metal layer of the upper-layer interconnection, and the embedded metal layer of the plug is made of Cu, Al, Ag, or W.
 15. A semiconductor device according to claim 12, wherein the embedded metal layer of the lower-layer interconnection, the embedded metal layer of the upper-layer interconnection, and the embedded metal layer of the plug are made of a material in which principal component is Cu.
 16. A semiconductor device comprising: a first interlayer insulating film formed on a semiconductor substrate; a first plug formed in a first via hole formed in the first interlayer insulating film; a second interlayer insulating film formed on the first interlayer insulating film and the first plug; a normal interconnection formed in a first groove formed in the second interlayer insulating film and connected to the first plug; a second plug formed on the normal interconnection formed in the second interlayer insulating film; and a dummy interconnection formed in a second groove formed in a region of the second interlayer insulating film, which corresponds to other region than those where the first plug and the second plug are formed, the dummy interconnection being connected to a first embedded metal of the normal interconnection, wherein the dummy interconnection has a width which is smaller than a minimum width of a minimum width interconnection.
 17. A semiconductor device according to claim 16, wherein the normal interconnection is made of a first barrier metal layer and the first embedded metal layer and the dummy interconnection is made of a second barrier metal layer and a second embedded metal layer.
 18. A semiconductor device according to claim 17, wherein the barrier metal layer of the normal interconnection and the barrier metal layer of the dummy interconnection are made of Ti or TiN.
 19. A semiconductor device according to claim 17, wherein the embedded metal layer of the normal interconnection and the embedded metal layer of the dummy interconnection consist are made of Cu, Al, Ag, or W.
 20. A semiconductor device according to claim 17, wherein the embedded metal layer of the normal interconnection and the embedded metal layer of the dummy interconnection consist are made of a material whose principal component is Cu. 